Effect of dietary supplementation with vitamin E on characteristics of vacuum‐packed lamb

The effect of dietary vitamin E supplementation on lamb during vacuum‐packed storage was studied. Thirty‐six weaned male Manchego breed lambs were offered four dietary treatments (20, 270, 520 and 1020 mg vitamin E kg^?1 feed). Lambs were fed the vitamin E‐supplemented diet from 13 until 26 kg live weight. Pieces of M. longissimus dorsi were stored under vacuum at 2 ± 1 °C in the dark and meat quality was assessed after 5, 14 and 28 days of storage. Dietary supplementation significantly increased the α‐tocopherol concentration in the muscle (P < 0.001). Initially, lipid oxidation, meat colour and bacterial load were similar in all groups. In meat of non‐supplemented lambs the thiobarbituric acid reactive substance value increased throughout storage, whereas in meat of supplemented lambs it did not increase. Meat pigments and discolouration proportion were significantly affected by storage time (P < 0.001). The bacterial load was low initially, but after 28 days of storage it was close to 7 log₁₀ colony‐forming units (cfu) cm^?2 and Enterobacteriaceae surpassed the limit of acceptability of 2.5 log₁₀ cfu cm^?2, making the lamb unsuitable for human consumption. Meat of supplemented lambs displayed less lipid oxidation than that of their non‐supplemented counterparts, while meat colour and bacterial load were not affected by supplementation. Copyright © 2007 Society of Chemical Industry     

钙离子协同溶氧提高重组β-CGT酶的可溶性表达量

环糊精葡萄糖基转移酶(Cyclodextrin glycosyltransferase,简称CGT酶)能够通过环化反应生成环糊精,但天然菌株发酵产酶的水平较低,使得环糊精的生产成本居高不下,因此旨在通过异源表达以及发酵优化策略来提高CGT酶的表达量。首先将来源于Bacillus xiaoxiensis STB08的cgt基因插入质粒pET-20b(+)中,在宿主菌Escherichia coli BL21(DE3)中进行分泌表达,在适宜的培养基中发酵96 h后,胞外酶活为34.66 U/mL。然后对发酵条件进行优化,改变溶氧以及添加一定终浓度的Ca2+可使酶活提高到66.86 U/mL及83.15 U/mL,且溶氧与Ca²⁺协同作用可使酶活提高到105.69 U/mL,相比于优化发酵条件之前提高了204.93%。最后通过蛋白质定位分析及流式细胞分析对溶氧及添加Ca²⁺影响发酵水平的机理进行了研究。结果表明,较低的溶氧能够减少重组大肠杆菌包涵体的形成,且溶氧较低时细胞活性较高,但溶氧过低时菌体浓度太低,不能满足菌体正常生长及代谢的需求。而添加Ca²⁺能够减少包涵体的形成,同时Ca²⁺对细胞有较好的保护作用,因此,在溶氧以及Ca²⁺的协同作用下,能够保证菌体的高生长浓度,且Ca²⁺能够增加细胞透性并保护细胞,使得活细胞数目显著增多。该研究提高了CGT酶在大肠杆菌中的可溶性表达量,为该酶的工业化生产提供了新的策略及方法,也可为相关酶的发酵优化提供参考。     

Microbiological characteristics of poultry patties in relation to packaging atmospheres

Microbial characteristics under different atmospheres (vacuum, air, MAP₁: 80% O₂/20% CO₂ and MAP₂: 5% O₂/65% N₂/30% CO₂) of poultry patties made of a mixture of ostrich, chicken and turkey meat were evaluated. The meat preparations were examined for changes in pH, colour properties (CIE L*, a*, b*), headspace composition, and bacterial counts (total viable cell, psychrotrophs, Enterobacteriaceae, lactic acid bacteria, Staphylococcus spp., Brochothrix thermosphacta, Pseudomonas spp.). The use of a high O₂ atmosphere (MAP₁) quickly leads to a loss of the appealing red colour. A limited alteration occurred with use of MAP₂ and vacuum. For total viable counts a cell load higher than 8 log cfu g^?1 for the samples packaged in air, MAP₁ and MAP₂ at the end of storage was observed. Whereas, for the vacuum packed samples the cell load never reached values higher than 8 log cfu g^?1. Enterobacteriaceae, B. thermosphacta and Pseudomonas spp. cell load was less with the vacuum (7.60, 5.06 and 7.17 log cfu g^?1, respectively) and MAP₂ packaging (7.08, 5.60 and 7.40 log cfu g^?1, respectively). However, the high microbial loads suggest that an improvement of the microbiological quality of poultry meat is necessary if the producers are going to propose this new meat preparation on the market.     

Effect of in vitro gastro-pancreatic digestion on antioxidant activity of low-molecular-weight (<3.5 kDa) peptides from dry-cured pork loins with probiotic strains of LAB

The antioxidant properties of low-molecular-weight peptides (<3.5 kDa) obtained from the dry-cured pork loins inoculated with probiotic and potentially probiotic lactic acid bacterial strains were tested after two-stage enzymatic hydrolysis under in vitro conditions. The water soluble fraction (WSF) was found to be a better substrate for enzymatic hydrolysis by proteolytic enzymes, especially when they were extracted from the meat product after 12 months of ageing. Furthermore, protein hydrolysates extracted from the salt soluble fraction (SSF) exhibited better or similar ABTS free radical scavenging activity and Fe²⁺-chelating activity than those extracted from WSF (despite their less quantity). Moreover, both SSF and WSF exhibited weak ferric-reducing antioxidant activity after two-step enzymatic hydrolysis (A₇₀₀ averaged 0.138 for the WSF and 0.088 for the SSF). These results might be useful to the meat-processing industry in developing innovative and functional meat products.     

The effect of certain amino acids and browning inhibitors on the ‘black spot’ phenomenon produced by Carnimonas nigrificans

Black spots are sometimes observed in fermented sausages and raw cured meat products, with resultant economic loss. The effect brought about by some amino acids in the development of this browning was evaluated, in aerobiosis at 30 °C and 90–95% RH, in a pork meat mixture with glucose, NaCl and inoculated with Carnimonas nigrificans CTCBS1^T at 1.0 × 10⁷ CFU g⁻¹. Amino acids and alternative substances to bisulphite and nitrite as preventative agents were studied for their effect on the browning reaction. The effect of NaCl concentration on browning and on the growth of Carnimonas nigrificans CTCBS1^T was also evaluated. Glycine, L ‐arginine, L ‐glutamine and L ‐monosodium glutamate were the amino acids that significantly decreased the L values and increased the browning scores in comminuted meat which was mixed with 40 gkg⁻¹ NaCl and 20 gkg⁻¹ D ‐(+)‐, glucose and inoculated with Carnimonas nigrificans CTCBS1^T. N‐acetyl‐L ‐cysteine, L ‐cysteine, potassium metabisulphite and propil‐3, 4, 5‐trihydroxybenzoate prevented browning at 10 and 5 gkg⁻¹. The optimum concentration of NaCl for the growth of Carnimonas nigrificans CTCBS1^T was 40 gkg⁻¹. © 2000 Society of Chemical Industry     

Rapid p-Nitroaniline Test for Assessing Microbial Quality of Refrigerated Meat

The p-nitroaniline test, a rapid method to estimate microbial quality of refrigerated meat, was applied to many retail meat samples from several animal species to confirm its applicability. This method allows determination of psychotroph levels between 10⁴ and 10⁸ CFU/cm² in about 2.5 hr. A good correlation was found (r = 0.88, p < 0.001) between this method and the standard plate count technique. Because of the yellow color of the p-nitroaniline released during reaction, bacterial loads higher than 10^s CFU/cm² develop a color intense enough to be detected visually.     

The rheological properties of exudates from cured porcine muscle: effects of added non‐meat proteins

Meat exudates were collected from massaged cured porcine M semimembranosus using a model massaging unit. Exudates were used to observe changes in gelation properties due to the incorporation of commercially available non‐meat proteins. These included: soya isolate (90%), sodium (Na) caseinate (85%) and high gelling whey protein concentrates (WPCs, A‐35%, B‐75% and C‐β‐lactoglobulin (55%), as well as a regular 76% protein, WPC D. Compositional analysis ( n=6) showed that incorporation of non‐meat proteins significantly (P<0.05) increased the protein concentration of test exudates in all cases compared to controls. The viscoelastic properties of control and test meat exudate samples (n=6) were analysed using control stress rheology in oscillatory mode. All exudates were heated from 20 to 80°C at 1°C min⁻¹, and subsequently cooled after 30 min back down to 20°C at 1°C min ⁻¹. Addition of WPCs at a 1, 2 and 3% residual powder level and soya isolate at a 1% residual level, resulted in increased storage modulus G′ (Pa) values compared with controls. A 1% residual level of Na caseinate was detrimental to meat exudate gelation, resulting in lower final G′ (Pa) values than those observed for the control. © 1999 Society of Chemical Industry     

Stability of two Ca2+-dependent neutral proteinases and their specific inhibitor during post-mortem storage of rabbit skeletal muscle

The variation in the amounts of the two forms of Calcium Activated Neutral Proteinase (high Ca²⁺ requiring and low Ca²⁺ requiring forms) and their specific inhibitor was determined during storage of skeletal muscle at 4°C for 0, 1, 3 and 6 days. Whereas the activity of the high Ca²⁺ requiring form remained nearly constant during this period, there was a progressive decrease in the levels of both the low Ca²⁺ requiring form and the specific inhibitor. The effect of different Ca²⁺ concentration on the two purified forms of the enzyme in the presence and absence of the inhibitor was also examined. Both enzyme forms were labile to preincubation at 30°C without inhibitor in 3 mmol litre^?1 Ca²⁺ whereas in 50 μmol litre^?1 Ca²⁺ only the low Ca²⁺ requiring form was inactivated, i.e. at a concentration which can be reached in muscle cells during contraction or after death of the animal. When the specific inhibitor was added, preincubation in 3 mmol litre^?1 Ca²⁺ did not affect either enzyme form since they were found to retain full activity on subsequent removal of the inhibitor. A possible role for the Calcium Activated Neutral Proteinases in the development of meat tenderness is discussed.     

Modeling the Transfer of Salmonella Enteritidis during Slicing of Ready‐to‐Eat Turkey Products Treated with Thyme Essential Oil

The increased demand for low‐sodium ready‐to‐eat (RTE) meat products highlights the need for new strategies to ensure food safety. The application of essential oils (EOs) as natural antimicrobials in the meat industry has been suggested to prevent or control cross‐contamination during meat processing operations. This work aims to quantify and model the transfer of Salmonella Enteritidis during the slicing procedure of RTE turkey products treated with thyme essential oil (TEO) at a concentration of 0.1% (v/w). Two products were subjected to the slicing procedure with slicer blades inoculated with S. Enteritidis at 10⁸ cfu/mL. The Weibull and modified Weibull predictive models were fitted to the transfer data. Twenty slices were sampled and showed positive with bacteria, indicating cross‐contamination. The number of cells transferred per slice decreased logarithmically during the assays. The transfer models, based on the Weibull model, were suitable to describe the bacterial transfer trend on slices in most cases. TEO treatment reduced the transfer of Salmonella on a preservative free RTE turkey product. The predictive models obtained in this study can help food‐quality staff and managers on the design and assessment of processes to guard RTE turkey products against Salmonella. This work supports the addition of EOs to reduce microbial risk in RTE meat products.     

Influence of different spices on the microbial reduction and storability of laboratory-processed tomato ketchup and minced meat

At 1% (w/w) each of 6 non-commercial spices (Xylopia aethiopica, Aframomum melegueta, Monodoran myristica, Piper guineense, Icacina spp and Congronema latifolia) when added to laboratory-processed tomato ketchup and minced meat reduced spoilage microbial populations to different levels. Tomato ketchup spiced with M. myristica remained sterile after 24 h incubation at room temperature (26 ± 2 °C) whilst control samples had bacterial and yeast counts of 1.5 ± 10⁷ cfu/g and 2.0 ± 10⁵ pro-pagules/g, respectively. X. aethiopica also reduced bacterial populations in tomato ketchup. In spiced minced meat, only X. aethiopica and C. latifolia showed an inhibitory effect on yeasts. Other spices used were not or relatively less effective against bacteria and yeasts.     

Formation of selected biogenic amines in carp meat

Changes in biogenic amine content in carp (Cyprinus carpio) muscle were studied. Fish halves and minced fish meat were stored at 3 and 15 °C. Both the temperature of storage and the type of meat processing had statistically important effects on the amine content. In another set of experiments, temperature and the preservative effects of Purac at various concentrations were tested. Purac can extend the shelf‐life of fish halves stored at 3 °C by about 5 days. Putrescine concentration is proposed as a chemical indicator of carp meat quality. Decomposition is apparent when the putrescine content in the meat exceeds 20 mg kg^?1. © 2002 Society of Chemical Industry     

Biosensors fob food industry

Novel biosensor systems were constructed for food industry. In order to determine fish freshness, a multifunctional enzyme sensor system was developed by combining a double membrane consisting of a 5'‐nucleotidase membrane and a nucleoside phosphorylase‐xanthine oxidase membrane with an oxygen electrode. Each nucleotide concentration was determined as the current decreased. One assay was completed within 20 min. Good comparative results were observed between the KI values determined by the sensor proposed and by the conventional method. An enzyme sensor for meat freshness consisted of a monoamine oxidase‐collagen membrane and an oxygen electrode. The response time of the electrode was 4 min. A linear relationship was observed between the amine (tyramine) concentration in the range 50–200 μM and the difference in current. Monoamine in meat extract was determined by the enzyme sensor. Micro‐glutamate sensor was constructed using silicon fabrication technology. Calibration curve for glutamate sensor was obtained in a glutamate concentration range between 5–50 mM. Moreover, an immuno sensor based on piezoelectric crystal was applied to the determination of toxic bacterium C. albicans. The frequency shift is correlated with C. albicans concentration in the range 10⁶ 5×10⁸ cell/ml.     

Evaluation of sodium dichloroisocyanurate treatment on recovered concentrations of Salmonella enterica,Escherichia coli O157:H7, and Listeria monocytogenes from cattle hide surfaces and culture medium

A major concern of the cattle industry is cross-contamination of meat with pathogens. Cattle are exposed to fecal material, mud, and other contaminants which harbor pathogens that can be shed onto meat and meat processing equipment. Due to increased chances of meat contamination during processing, new antimicrobial formulations for carcass washing before hide removal needs to be identified and tested. Sodium dichloroisocyanurate (SDIC) has biocidal properties and belongs to the N-halamine group of compounds. Disk diffusion assays revealed, 1,000 ppm SDIC effectively reduced pathogen concentrations. SDIC was evaluated for its effects on pathogens in Tryptic Soy Broth and results revealed that 1,000 ppm SDIC had a strong correlation with time and treatment with no bacterial growth in log CFU ml⁻¹ observed at the lowest detection level. Treatment of inoculated hides with 1,000 ppm SDIC for 5 min resulted in reduction of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes at 1.97, 2.02, and 2.84 log CFU cm⁻², respectively.     

Antioxidant activity of pomegranate rind powder extract in cooked chicken patties

The radical scavenging activity, reducing power and phenolic composition of pomegranate rind powder extract (RP) were determined and antioxidant properties of RP was evaluated in cooked chicken patties compared with vitamin C (VC) during refrigerated storage. Freshly minced chicken meat were assigned to one of the following six treatments: control (meat without any antioxidant); RP 5, RP 10, RP 15 and RP 20 (5, 10, 15 and 20 mg equivalent RP phenolics 100 g^?1 meat, respectively) and VC 50 (50 mg VC 100 g^?1 meat). The RP exhibited significantly (P < 0.05) higher reducing power and 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity. Incorporation of RP into chicken patties significantly (P < 0.05) reduced the HunterLab L* values compared with control and VC patties. Total phenolic content (as tannic acid equivalent) significantly (P < 0.05) increased from 308 in control to 441 μg g^?1 in RP 20 patties. Addition of RP to chicken patties did not affect any of the sensory attributes. The values of thiobarbituric acid reactive substances were significantly (P < 0.05) reduced from 1.530 in control patties to 0.135 mg malonaldehyde kg^?1 samples in RP patties. Pomegranate rind powder extract treatment (RP 10, RP 15 and RP 20) substantially inhibited (P < 0.05) lipid oxidation in cooked chicken patties to a much greater extent than VC treatment. Therefore, pomegranate rind powder can be utilized as an excellent natural antioxidant source.     

Bacteriological quality of sheep meat in Mhow town of India

The purpose of this study was to investigate bacterial load in ready‐to‐sale sheep meat with special reference to Salmonella. Samples were collected from 100 sheep carcasses from retail meat shops in domestic markets. On carcasses, where bacterial counts were obtained, the mean of the log₁₀ aerobic plate count was 7.26 cfu g^?1, and that of total coliform count and total Escherichia coli count was 4.11 log₁₀ cfu g^?1 and 3.03 log₁₀ cfu g^?1, respectively. All the samples (100) were found positive for coliforms, 49.0% were positive for E. coli and 3.0% were positive for Salmonella. The isolates were serotyped as Salmonella infantis having antigenic structure 6, 7: r: 1, 5. Antibiogram revealed highest (100.0%) sensitivity towards amikacin, ceftriaxone, ciprofloxacin, chloramphenicol, colistin sulphate, gentamicin and nalidixic acid followed by cefuroxime and tetracycline (66.67% each) and cotrimoxazole (33.33%). All the strains were resistant to ampicillin.     

Bioproduction of mushroom mycelium of Agaricus bisporus by commercial submerged fermentation for the production of meat analogue

BACKGROUND As worldwide interest in healthy and delicious meat analogues increases, the texture of these products has become an important indicator of quality. Mycoprotein as fungal mycelium could provide a distinctive chewing sensation; however, the unfavorable consumer perception of fungal mycelium demands the production of meat analogues with true mushroom mycelium. RESULTS: The industrial and economical bioprocess was developed using an inexpensive medium (30 g L^?1 sugar cane extract (SCE), 10 g L^?1 NaNO₃ and 5 g L^?1 yeast extract) and A. bisporus Suksung. The SCE was maintained at around 10 g L^?1 to minimize osmotic shock. The maximum mycelium production of 15.0 g L^?1 (dry weight) was reached within 4 days. Scanning electron microscopic analysis showed fibrous and directional structure rather than a more typical pellet structure. Meat analogues with mushroom mycelium had better textural properties, being higher in hardness, springiness, and chewiness and with preferable umami characteristics compared to meat analogues utilizing soy protein. The overall acceptance of meat analogues prepared with mycelium and soy protein, and a ground beef patty, were 5, 2 and 10, respectively. CONCLUSION: The development of an industrial bioprocess for A. bisporus mycelium allowed the production of a highly acceptable meat analogue having not only superior textural properties but also umami characteristics when compared to that of soy protein. Copyright © 2011 Society of Chemical Industry     

Effects of copper on the post acidification of fermented milk by St. thermophilus

Abstract: As an initial investigation of using Cu²⁺ to control post acidification, the fermentation time, pH and the viable counts of bacteria of fermented milk during fermentation and storage were studied. Streptococcus thermophilus was used as the starter culture to ferment the whole milk. Cu²⁺ was added to whole milk at a concentration ranging from 1.25 to 20 mg/kg before fermentation. It was observed that increasing the concentration of Cu²⁺, the fermentation time of yoghurt was prolonged, while the post acidification of fermented milk was decreased during storage. The results showed that Cu²⁺ at the concentration of 1.25 mg/kg could reduce the post acidification of fermented milk effectively and showed no significant effect on neither the fermentation time nor the viable counts of S. thermophilus (P > 0.05) compared with the control sample. These findings indicated that Cu²⁺ could be used as a potential additive to inhibit the post acidification of yoghurt. Practical Application: Adding copper to milk has an effect on fermented milk products such as yoghurt. Increasing the concentration of Cu2⁺ decreased the post acidification of fermented milk. The fermentation time is prolonged with the increase of Cu2⁺ concentration. Cu2⁺ at 1.25 mg/kg exhibited inhibition on post acidification and had no significant effect on fermentation time and the viable counts of fermented milk.     

Bacteriocidal and Mutagenic Effects of Ozone on Shrimp(Penaeus monodon) Meat

We examined solubility and stability of ozone in shrimp-meat extract (SME), bacteriocidal effect of ozone on shrimp-meat microorganisms, mutagenicity of ozonated shrimp meat, and ozonolysis of DNA. The saturated concentration (1.4 mg-O₃/L) of ozone in SME was lower than in 2% saline or distilled water at 5 and 25°C. Upon standing for 25 min after ozonation, ozone exhibited the same decomposition rate (2.7%/min) in 5 and 25°C SME. Among 9 bacterial strains tested, Salmonella typhimurium was more resistant to ozone in shrimp meat. Mutagen was not detected in shrimp meat when it was ozonated in saline. Ozone in saline (less than 5 mg-O₃/L) could lyse M13 RF DNA in Escherichia coli and single-stranded DNA in phage M13 outside bacterial cell, within 30 min.     

Inhibition of Brochothrix thermosphacta in broths and pork by myristoyl-L-methionine

The antibacterial properties of myristoyl-L-methionine (Myr-Met) were examined in commercial broths (APT, cooked meat medium), aqueous extracts of pork muscle, pork muscle slurries and at the surface of pork muscle discs inoculated with Brochothrix thermosphacta. Broths and muscle substrates were inoculated with B. thermosphacta to give an initial concentration of about 4 log cfu ml⁻¹or cm²and bacterial growth in the presence or absence of Myr-Met was determined by plate counts during 9 days of aerobic incubation at 4°C. In an aqueous muscle extract and APT broth Myr-Met was bactericidal at concentrations of 5 and 50 μg ml⁻¹, respectively, reducing B. thermosphacta to below recoverable levels (<1 log cfu ml⁻¹). Efficacy was diminished in substrates containing muscle or meat particles and 500 μg ml⁻¹Myr-Met only produced a transient bacteriostatic effect in pork muscle slurries. A concentration of 500 μg ml⁻¹Myr-Met was without effect upon the growth of B. thermosphacta in a commercial cooked meat medium or on the surface of inoculated pork muscle discs. To produce a significant inhibition of B. thermosphacta growth on pork muscle tissue it was necessary to increase the concentration of Myr-Met to 5000 μg ml⁻¹, using the sodium salt of Myr-Met to permit solublization. A mechanism to prevent Myr-Met inactivation in meat is necessary if Myr-Met is to be of practical value as a preservative.     

ALUMINUM STABILIZES TURMERIC IN PICKLE BRINE AGAINST DECOMPOSITION BY LIGHT,HEAT AND PEROXIDASE1

Turmeric in solutions typically used for cucumber pickle manufacturing was protected by Al³⁺ from decomposition caused by fluorescent light, heat and peroxidase. Levels of 1.3–1.5 mM Al³⁺ significantly reduced light-and peroxidase-catalyzed decomposition of turmeric, and the amount of retardation increased with increasing Al³⁺ concentration. Alone, neither peroxidase nor hydrogen peroxide affected turmeric; however when combined, turmeric was rapidly destroyed. Peroxidase destruction of turmeric was uncompetitively inhibited by Al³⁺. Turmeric decomposition increased with increasing temperature from 20 to 90°C. No thermal destruction of turmeric was observed in the presence of 2 or 4 mM Al³⁺.